Killer Cages are common in variant puzzles. Although some cages have been distorted and don’t follow standard “Killer Cages” rules, most are standard.

Digits in cages do not repeat, and sum to the total in the top-left corner of the cage, if given. If not given, they just do not repeat.

There are variants like Semi-Killer cages and Gravity Cages that use cages for their own purposes, but generally, Killer Cages just have the two conditions: no repeats, sum to a total.